It is always a gamble, Pete whether different birds will get on with each other or not. Mine don't, my cockatiel keeps coming to my grey but he just wants to bite the cockatiel, so they have to walk in turns. But I have heard recently of a few cockatiels and greys living in peace together. One way or the other, this friendship always has an element of danger, a grey can potentially kill a cockatiel with its strong beak Maybe your friend should consider a smaller parrot, like a conure or a caique, they are all lovely and just as joyful to have as Greys, and sometimes even more as they ate not as prone to psychological problems